Alternatively, certain discrepancies in reported markers might be due to methodological differences in the design of the studies analyzing established ovarian cancer cell lines versus primary fresh material, selection criteria of patient samples etc. For example, it has recently been demonstrated that in vitro cultivation of fresh cells isolated from primary tumors in the presence of fetal calf serum leads to a gradual loss of the stem cell markers CD133, ALDH1, CD24, CD44 and CD117 [91]. This evidence concerns the gene CD44 and ovarian carcinoma.